Have a walnut. Speak your mind. Plan ahead. Tiny but powerful life tweaks that will make you happier, healthier, and—yes!—better.

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Brush Your Teeth with Your Other Hand

Using your nondominant hand to do simple chores can improve your mood and your memory; that's because the action stimulates the production of brain-derived neurotrophic factor (BDNF), a protein that encourages the growth of neurons linked to long-term memory and mood. "When you're depressed or under stress, your brain's production of BDNF plummets," says Moses Chao, PhD, professor of neuroscience and psychiatry at New York University School of Medicine. (One of the lesser-known effects of antidepressants, he says, is to raise the levels of BDNF.) Anything unexpected—smelling rosemary first thing in the morning, for example—can activate BDNF.